1. Field of the Invention
The invention is concerned with guns for thoroughly intermixing mutually soluble liquid reactants while pourably delivering the resulting mixture at substantially atmospheric pressure. More particularly the invention is concerned with a gun adapted to intermix an isocyanate with a polyhydroxy resin (a polyol), at least one of said isocyanate and said polyol including a catalyst therewith and to pourably deliver the resulting mixture at substantially atmospheric pressure and before any significant amount of reaction has occurred between the isocyanate and the polyol.
2. Prior Art
Prior art guns in which isocyanates have been intermixed with polyols and a catalyst for the reaction therebetween have generally been of the spray gun variety. That is, sufficient of the catalyst has been present so that the reaction between the isocyanate and the polyol proceeds within the mixing chamber of the gun at a very rapid rate thereby generating large quantities of gas whereby the reactants are thoroughly intermixed with each other due both to the violence of the reaction and to the fact that they are expelled from the gun through an orifice or nozzle in a foamy spray by the high pressures and gas formation involved. Examples of such prior art devices may be found, for example, in each of U.S. Pat. Nos. 3,366,337; 3,623,669; 3,690,557; 3,799,403 and 3,850,371.
When a gun has been desired for the mixing of an isocyanate with a polyol in the presence of a relatively small amount of catalyst or of a relatively slow acting catalyst whereby the mixture exits from the gun before significant foaming reaction can occur within the gun to thoroughly mix the components thereof, it has been necessary to provide a mixing chamber within the gun which includes baffles and other mechanical means therein to aid in the intermixing of the isocyanate with the polyol. This has led to a number of problems not the least of which is the expense of fabricating the complicated structure involved and the necessity for frequent cleaning of the baffles. In addition, it was generally necessary for the mixture to exit the gun at a pressure above substantially atmospheric in order to provide the desired mixing action.